For decades, chemists and dental product manufacturers have attempted to develop a soft liner for dentures and/or prosthetic devices to absorb the pressure on the wearer's gums on the tissue side of these devices. The discomfort and often pain to the denture wearer necessitates shaping the hard acrylic or other surfaces so as to allow perfect fit.
Inasmuch as dimensional change in the size and shape of the jaw occurs in all denture wearers, (especially in older people or in post-operative cases when swelling subsides), a soft, flexible, custom fit, cushion like liner permanently bonded to the prosthesis is needed.
Whereas prior products exist intended to accomplish the above objectives, all have different problems associated with their application. In particular, the non-compatible soft liners such as the silicon or rubber-based materials must be "glued" onto the hard acrylic surface with an adhesive bonding agent, and often this bonding agent contains a methyl methacrylate monomer. Over time, these adhesive agents leach into the soft material and harden it.
Moreover, adhesives harden and crack at the "seam" at the junction where the soft material is glued on to the hard material. Lactic acid, alcohol, and/or medication accelerate this separation. At this point, bacteria, fungus, odor, debris, and stain penetrate the soft liners. This natural absorption degrades the soft liners creating a hardening, peeling, and medically unstable condition.
In addition, the repair process of other existing materials is difficult since the base material either flakes off when trimmed, or it cannot be re-molded with standard dental tools. Also, to "glue" small sections of liner onto thin acrylic edges is difficult or impossible as the liners break off under the constant pressure which occurs in the oral cavity.
There are various products which use heat or light to cure resins of various formulation onto prosthetic devices. Almost all of these formulations require a bonding agent which run into the same problems as mentioned above. Many of these finished liners absorb liquids accelerating their deterioration.
Another category of liners which are temporary in nature are known as "tissue conditioners". These gels or stick-on resins last only weeks or a few months before they peel-off. They usually are soft due to high porosity, and thus they absorb liquids which ultimately breakdown the materials. The absorbency allows bacteria and odor buildup in the mouth, an undesirable result.
An elastomeric material is available which overcomes many of the disadvantages of the prior indicated materials. This material is a methyl methacrylate-free soft material which effectively fuses to acrylic surfaces without a gluing agent. The material is formed by blending a powder component of polyethylmethacrylate and a liquid component of Di-n-butyl phthalate, ethyl acetate and ethyl alcohol which are mixed together until all of the powder particles are totally moistened. The resultant mixture is then applied as a reline material for dentures by being coated on the denture surface. A polyvinyl chloride/polyvinyl acetate copolymer dissolved in a methyl ethyl ketone solvent forms a sealer component which is then applied over the liner to create a nonabsorbent surface seal.